Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

The microstructure and phase composition of the high-content Al₂O₃-Y₂O₃-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si₃N₄ equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si₃N₄ grains, higher hardness of 1800 HV, density of 3.25 g/cm³, and Young's modulus 300 GPa SPSed at 1650 °C was also reviewed.